Ferritic alloy

ABSTRACT

A ferritic alloy comprising the following elements in weight % [wt %] C 0.01 to 0.1; N: 0.001 to 0.1; O: ≤0.2; Cr 4 to 15; Al 2 to 6; Si 0.5 to 3; Mn: ≤0.4; Mo+W≤4; Y≤1.0; Sc, Ce, and/or La≤0.2; Zr≤0.40; RE≤0.4; balance Fe and normal occurring impurities and also fulfilling the following equation has to be fulfilled: 0.014≤(Al+0.5SQ (Cr+10Si+0.1)≤0.022.

TECHNICAL FIELD

The present disclosure relates to a ferritic alloy according to thepreamble of claim 1. The present disclosure further relates to use ofthe ferritic alloy and to objects or coatings manufactured thereof.

BACKGROUND AND INTRODUCTION

Ferritic alloys, such as FeCrAl-alloys comprising chromium (Cr) levelsof 15 to 25 wt % and aluminium (Al) levels from 3 to 6 wt % are wellknown for their ability to form protective α-alumina (Al₂O₃), aluminiumoxide, scales when exposed to temperatures between 900 and 1300° C. Thelower limit of Al content to form and maintain the alumina scale varieswith exposure conditions. However, the effect of a too low Al level athigher temperatures is that the selective oxidation of Al will fail andless stable and less protective scales based on chromium and iron willbe formed.

It is commonly agreed that FeCrAl alloys will normally not form theprotective α-alumina layer if exposed to temperatures below about 900°C. There have been attempts to optimize the compositions of FeCrAlalloys so that they will form the protective α-alumina at temperaturebelow about 900° C. However, in general, these attempts have not beenvery successful because the diffusion of oxygen and aluminium to theoxide-metal interface will be relatively slow at lower temperatures andthereby the rate of formation of the alumina scale will be low, whichmeans that there will be a risk of severe corrosion attacks andformation of less stable oxides.

Another problem arising at lower temperature, i.e. temperatures below900° C., is a long term embrittlement phenomena arising from a lowtemperature miscibility gap for Cr in the FeCrAl alloy system. Themiscibility gap exists for Cr levels above approximately 12 wt % at 550°C. Recently, alloys with lower Cr levels of about 10 to 12 wt % Cr havebeen developed in order to avoid this phenomenon. This group of alloyshas been found to work very well in molten lead at controlled and lowpressure O₂.

EP 0 475 420 relates to a rapidly solidified ferritic alloy foilessentially consisting of Cr, Al, Si, about 1.5 to 3 wt % and REM (Y,Ce, La, Pr, Nd, the balance being Fe and impurities. The foil mayfurther contain about 0.001 to 0.5 wt % of at least one element selectedfrom the group consisting of Ti, Nb, Zr and V. The foil has a grain sizeof not more than about 10 μm. EP 075 420 discusses Si additions in orderto improve the flow properties of the alloy melt but the success waslimited due to reduced ductility.

EP 0091 526 relates to thermal cyclic oxidation resistant and hotworkable alloys, more particularly, to iron-chromium-aluminium alloyswith rare earth additions. In oxidation, the alloys will produce awhisker-textured oxide that is desirable on catalytic convertersurfaces. However, the obtained alloys did not provide a hightemperature resistance.

Hence, there is still a need to further improve the corrosion resistanceof ferritic alloys so that they can be used in corrosive environmentsduring high temperature conditions. The aspects of the presentdisclosure are to solve or at least reduce the above-mentioned problems.

SUMMARY OF THE DISCLOSURE

The present disclosure therefore relates to a ferritic alloy, which willprovide a combination of good oxidation resistance and an excellentductility, comprising the following composition in weight % (wt %):

-   -   C 0.01 to 0.1;    -   N: 0.001-0.1;    -   O: ≤0.2;    -   Cr 4 to 15;    -   Al 2 to 6;    -   Si 0.5 to 3;    -   Mn: ≤0.4;    -   Mo+W≤4;    -   Y≤1.0;    -   Sc, Ce, and/or La≤0.2;    -   Zr≤0.40;    -   RE≤1.0;    -   balance Fe and normal occurring impurities and also fulfilling        the following equation has to be fulfilled:

0.014≤(Al+0.5Si)(Cr+10Si+0.1)≤0.022.

Thus, there exists a relationship between the content of Cr and Si andAl in the alloy according to the present disclosure, which if fulfilledwill provide an alloy having excellent oxidation resistance andductility and also a reduced brittleness in combination with increasedhigh temperature corrosion resistance.

The present disclosure also relates to an object and/or a coatingcomprising the ferritic alloy according to the present disclosure.Additionally, the present disclosure also relates to the use of theferritic alloy as defined hereinabove or hereinafter for manufacturingan object and/or a coating.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1a and FIG. 1b disclose the phases in Fe-10% Cr-5% Al vs. Si level(FIG. 1a ) and Fe-20% Cr-5% Al vs. Si level (FIG. 1b ). The diagram hasbeen made by using Database TCFE7 and Thermocalc software.

FIGS. 2a to e disclose polished sections of two alloys according to thepresent disclosure compared to three reference alloys after exposure to50 times 1 hour cycles at 850° C. exposed to biomass (wood pellets) ashcontaining large amounts of potassium.

DETAILED DESCRIPTION OF THE DISCLOSURE

As already stated above, the present disclosure provides a ferriticalloy comprising in weight % (wt %):

-   -   C 0.01 to 0.1;    -   N: 0.001-0.1;    -   O: ≤0.2;    -   Cr 4 to 15;    -   Al 2 to 6;    -   Si 0.5 to 3;    -   Mn: ≤0.4;    -   Mo+W≤4;    -   Y≤1.0;    -   Sc, Ce, and/or La≤0.2;    -   Zr≤0.40;    -   RE≤1.0;    -   balance Fe and normal occurring impurities and also fulfilling        the following equation has to be fulfilled:

0.014≤(Al+0.5Si)(Cr+10Si+0.1)≤0.022.

It has surprisingly been found that an alloy as defined hereinabove orhereinafter, i.e. containing the alloying elements and in the rangesmentioned herein, unexpectedly will form a protective surface layercontaining aluminium rich oxide even at chromium levels as low as 4 wt%. This is very important both for the workability and for the long termphase stability of the alloy as the undesirable brittle σ-phase, afterexposure for long time in the herein mentioned temperature range, willbe reduced or even avoided. Thus, the interaction between Si and Al andCr will enhance the formation of a stable and continuous protectivesurface layer containing aluminium rich oxide, and by using the aboveequation, it will be possible to add Si and still obtain a ferriticalloy which will be possible both to produce and to form into differentobjects. The inventor has surprisingly found that if the amounts of Siand Al and Cr are balanced so that the following condition is fulfilled(all the numbers of the elements are in weight fractions):

0.014≤(Al+0.5Si)(Cr+10Si+0.1)≤0.022,

the obtained alloy will have a combination of excellent oxidationresistance and workability and formability within the Cr range of thepresent disclosure. According to one embodiment,0.0155≤(Al+0.5Si)(Cr+10Si+0.1)≤0.021, such as0.016≤(Al+0.5Si)(Cr+10Si+0.1)≤0.020, such as0.017≤(Al+0.5Si)(Cr+10Si+0.1)≤0.019.

The ferritic alloy of the present disclosure is especially useful attemperatures below about 900° C. since a protective surface layercontaining aluminium rich oxide will be formed on an object and/or acoating made of said alloy, which will prevent corrosion, oxidation andembrittlement of the object and/or the coating. Furthermore, the presentferritic alloy may provide protection against corrosion, oxidation andembrittlement at temperatures as low as 400° C. as a protective surfacelayer containing aluminium rich oxide will be formed on the surface ofthe object and/or coating manufactured thereof. Additionally, the alloyaccording to the present disclosure will also work excellent attemperatures up to about 1100° C. and it will show a reduced tendencyfor long-term embrittlement in the temperature range of 400 to 600° C.

The present alloy may be used in the form of a coating. Additionally, anobject may also comprise the present alloy. According to the presentdisclosure, the term “coating” is intended to refer to embodiments inwhich the ferritic alloy according to the present disclosure is presentin form of a layer exposed to a corrosive environment that is in contactwith a base material, regardless of the means and methods to accomplishit, and regardless of the relative thickness relation between the layerand the base material. Hence, examples of this but not limited to is aPVD coating, a cladding or a compound or composite material. The aim ofthe alloy is that is should protect the material underneath from bothcorrosion and oxidation. Examples, but not limited to, of suitableobjects is a compound tube, a tube, a boiler, a gas turbine componentand a steam turbine component. Other examples include a superheater, awater wall in a power plant, a component in a vessel or a heat exchanger(for example for reforming or other processing of hydrocarbons or gasescontaining CO/CO₂), a component used in connection with industrial heattreatment of steel and aluminium, powder metallurgy processes, gas andelectric heating elements.

Furthermore, the alloy according to the disclosure is suitable to beused in environments having corrosive conditions. Examples of suchenvironments include but are not limited exposure to salts, liquid leadand other metals, exposures to ash or high carbon content deposits,combustion atmospheres, atmospheres with low pO₂ and/or high N₂ and/orhigh carbon activity environments.

Additionally, the present ferritic alloy may be manufactured by usingnormally occurring solidification rates ranging from conventionalmetallurgy to rapid solidification. The present alloy will also besuitable for manufacturing all types of objects both forged andextruded, such as a wire, a strip, a bar and a plate. The amount of hotand cold plastic deformation as well as grain structure and grain sizewill, as the person skilled in the art know vary between the forms ofthe objects and the production route.

The functions and effects of essential alloying elements of the alloydefined hereinabove and hereinafter will be presented in the followingparagraphs. The listing of functions and effects of the respectivealloying elements is not to be seen as complete as there may be furtherfunctions and effects of said alloying elements.

Carbon (C)

Carbon may be present as an unavoidable impurity resulting from theproduction process. Carbon may also be included in the ferritic alloy asdefined hereinabove or hereinafter to increase strength by precipitationhardening. To have a noticeable effect on the strength in the alloy,carbon should be present in an amount of at least 0.01 wt %. At too highlevels, carbon may result in difficulties to form the material and alsoa negative effect on the corrosion resistance. Therefore, the maximumamount of carbon is 0.1 wt %. For example, the content of carbon is0.02-0.09 wt %, such as 0.02-0.08 wt %, such as 0.02-0.07 wt % such as0.02-0.06 wt % such as 0.02-0.05 wt %, such as 0.01-0.04 wt %.

Nitrogen (N)

Nitrogen may be present as an unavoidable impurity resulting from theproduction process. Nitrogen may also be included in the ferritic alloyas defined hereinabove or hereinafter to increase strength byprecipitation hardening, in particular when a powder metallurgicalprocess route is applied. At too high levels, nitrogen may result indifficulties to form the alloy and also have a negative effect on thecorrosion resistance. Therefore, the maximum amount of nitrogen is 0.1wt %. Suitable ranges of nitrogen are for example 0.001-0.08 wt %, suchas 0.001-0.05 wt %, such as 0.001-0.04 wt %, such as 0.001-0.03 wt %,such as 0.001-0.02 wt %.

Oxygen (O)

Oxygen may exist in the alloy as defined hereinabove or hereinafter asan impurity resulting from the production process. In that case, theamount of oxygen may be up to 0.02 wt %, such as up to 0.005 wt %. Ifoxygen is added deliberately to provide strength by dispersionstrengthening, as when manufacturing the alloy through a powdermetallurgical process route, the alloy as defined hereinabove orhereinafter, comprises up to or equal to 0.2 wt % oxygen.

Chromium (Cr)

Chromium is present in the present alloy primarily as a matrix solidsolution element. Chromium promotes the formation of the aluminium oxidelayer on the alloy through the so-called third element effect, i.e. byformation of chromium oxide in the transient oxidation stage. Chromiumshall be present in the alloy as defined hereinabove or hereinafter inan amount of at least 4 wt % to fulfill this purpose. In the presentinventive alloy, Cr also enhances the susceptibility to form brittle aphase and Cr₃Si. This effect emerges at around 12 wt % and is enhancedat levels above 15 wt %, therefore the limit of Cr is 15 wt %. Also fromoxidation point of view, higher levels than 15 wt % will result in anundesirable contribution of Cr into the protective oxide scales.According to one embodiment, the content of Cr is 5 to 13 wt %, such as5 to 12 wt %, such as 6 to 12 wt %, such as 7 to 11 wt %, such as 8 to10 wt %.

Aluminium (Al)

Aluminium is an important element in the alloy as defined hereinabove orhereinafter. Aluminium, when exposed to oxygen at high temperature, willform the dense and thin oxide, Al₂O₃, through selective oxidation, whichwill protect the underlying alloy surface from further oxidation. Theamount of aluminium should be at least 2 wt % to ensure that aprotective surface layer containing aluminium rich oxide is formed andalso to ensure that sufficient aluminium is present to heal theprotective surface layer when damaged. However, aluminium has a negativeimpact on the formability and high amounts of aluminium may result inthe formation of cracks in the alloy during mechanical working thereof.Consequently, the amount of aluminium should not exceed 6 wt %. Forexample, aluminium may be 3-5 wt %, such as 2.5-4.5 wt %, such as 3 to 4wt %.

Silicon (Si)

In commercial FeCrAl alloys, silicon is often present in levels of up to0.4 wt %. In ferritic alloys as defined hereinabove or hereinafter, Siwill play a very important role as it has been found to have a greateffect on improving the oxidation and corrosion resistance. The upperlimit of Si is set by the loss of workability in hot and cold conditionand increasing susceptibility to formation of brittle Cr₃Si and a phaseduring long term exposure. Additions of Si therefore have to beperformed in relation to the content of Al and Cr. The amount of Si istherefore between 0.5 to 3 wt %, such as 1 to 3 wt %, such as 1 to 2.5wt %, such as 1.5 to 2.5 wt %.

Manganese (Mn)

Manganese may be present as an impurity in the alloy as definedhereinabove or hereinafter up to 0.4 wt %, such as from 0 to 0.3 wt %.

Yttrium (Y)

In melt metallurgy, yttrium may be added in an amount up to 0.3 wt % toimprove the adherence of the protective surface layer. Furthermore, inpowder metallurgy, if yttrium is added to create a dispersion oftogether with oxygen and/or nitrogen, the yttrium content is in anamount of at least 0.04 wt %, in order to accomplish the desireddispersion hardening effect by oxides and/or nitrides. The maximumamount of yttrium in dispersion hardened alloys in the form of oxygencontaining Y compounds may be up to 1.0 wt %.

Scandium (Sc), Cerium (Ce) and Lanthanum (La)

Scandium, Cerium, and Lanthanum are interchangeable elements and may beadded individually or in combination in a total amount of up to 02 wt %to improve oxidation properties, self-healing of the aluminium oxide(Al₂O₃) layer or the adhesion between the alloy and the Al₂O₃ layer.

Molybdenum (Mo) and Tungsten (W)

Both molybdenum and tungsten have positive effects on the hot-strengthof the alloy as defined hereinabove or hereinafter. Mo has also apositive effect on the wet corrosion properties. They may be addedindividually or in combination in an amount up to 4.0 wt %, such as from0 to 2.0 wt %.

Reactive Elements (RE)

Per definition, the reactive elements are highly reactive with carbon,nitrogen and oxygen. Titanium (Ti), Niobium (Nb), Vanadium (V), Hafnium(Hf), Tantalum (Ta) and Thorium (Th) are reactive elements in the sensethat they have high affinity to carbon, thus being strong carbideformers. These elements are added in order to improve the oxidationproperties of the alloy. The total amount of the elements is up to 1.0wt % such as 0.4 wt %/o, such as up to 0.15.

The maximum amounts of respective reactive element will depend mainly ontendency of the element to form adverse intermetallic phases.

Zirconium (Zr)

Zirconium is often referred to as a reactive element as since it is veryreactive towards oxygen, nitrogen and carbon. In the present alloy, ithas been found that Zr has a double role as it will be present in theprotective surface layer containing aluminium rich oxide therebyimproving the oxidation resistance and it will also form carbides andnitrides. Thus, in order to achieve the best properties of theprotective surface layer containing aluminium rich oxide, it isadvantageous to include Zr in the alloy.

However, Zr-levels above 0.40 wt % will have an effect on the oxidationdue to the formation of Zr rich intermetallic inclusions and levelsbelow 0.05 wt % will be too small to fulfill the dual purpose,regardless of the C and N content. Thus, if Zr is present, the range isbetween 0.05 to 0.40 wt %, such as 0.10 to 0.35.

Furthermore, it has also been found that the relationship between Zr andN and C may be important in order to achieve even better oxidationresistance of the protective surface layer, i.e. the alumina scale.Thus, the inventor has surprisingly found that if Zr is added to thealloy and the alloy also comprises N and C and if the followingcondition (the element content given in weight %) is fulfilled:

${{- 0.15} \leq {{Zr} - \frac{{4.7C} + {4N}}{0.62}} \leq 0.15},{{{{such}\mspace{14mu} {as}}\mspace{14mu}  - 0.15} \leq {{Zr} - \frac{{4.7C} + {4N}}{0.62}} \leq 0.10},{{{{such}\mspace{14mu} {as}}\mspace{14mu}  - 0.05} \leq {{Zr} - \frac{{4.7C} + {4N}}{0.62}} \leq 0.10},$

the obtained alloy will achieve a good oxidation resistance.

The balance in the ferritic alloy as defined hereinabove or hereinafteris Fe and unavoidable impurities. Examples of unavoidable impurities areelements and compounds which have not been added on purpose, but cannotbe fully avoided as they normally occur as impurities in e.g. thematerial used for manufacturing the ferritic alloy.

FIG. 1a and FIG. 1b shows that higher Cr in a Si-containing ferriticalloy is prone to form Si₃Cr inclusions and at 20% Cr also to promoteundesirable brittle σ-phase after exposure for long time in the focustemperature area. Although diagrams are only shown for two Cr levels, 10and 20%, the trend of embrittling phases increasing with higher Cr isclearly demonstrated Note the absence of σ-phase at 10% Cr and theincreasing amount of Cr₃Si phase at higher Si content at both Cr levels.Hence, these figures show that there will be problems when using Crlevels around 20%.

When the terms “≤” or “less than or equal to” are used in the followingcontext: “element≤number”, the skilled person knows that the lower limitof the range is 0 wt % unless another number is specifically stated.Further, the undefined article “a” does not exclude a plurality.

The present disclosure is further illustrated by the followingnon-limiting examples.

Examples

Test melts were produced in a vacuum melting furnace. The compositionsof the test melts are shown in table 1.

The obtained samples were hot rolled and machined to flat rods with across section of 2×10 mm. They were then cut into 20 mm long coupons andground with SiC paper to 800 mesh for exposure to air and combustionconditions. Some of the rods were cut to 200 mm long×3×12 mm rods fortensile testing at room temperature in a Zwick/Roell Z100 tensile testapparatus.

The results from exposure and tensile tests are shown in table 1.

The samples were tested for yield and rupture stress as well aselongation to rupture in a standard tensile test machine and the resultgiving >3% elongation to rupture is designated “x” in “Workable” columnof the table. The “x” therefore designates an alloy that is easily hotrolled and that shows ductile behavior at room temperature. In the“Oxidation” column, the “x” designates that the alloy forms a protectivealumina rich oxide scale at 950° C. in air and at 850° C. with biomassash deposit.

TABLE 1 Composition of the melts and the results of testing workabilityand oxidation an (x) designates a value between 3 and 6% elongation.Composition Melt-number Cr Al Si C N Zr Workable Oxidation 4785 5.2 4.00.03 0.020 0.012 0.296 x No Comparative 4784 5.2 6.0 0.02 0.025 0.0120.297 x No Comparative 4783 5.2 3.9 1.96 0.021 0.010 0.292 x X(disclosure) 4782 10.0 2.0 0.02 0.025 0.014 0.273 x No Comparative 478110.0 3.0 0.03 0.025 0.021 0.296 x No Comparative 4780 10.1 4.0 0.020.021 0.015 0.296 x No Comparative 4779 10.1 4.0 1.91 0.022 0.013 0.296x X (disclosure) 4778 10.2 5.9 0.11 0.018 0.012 0.294 x No Comparative4777 20.0 4.0 0.02 0.018 0.020 0.295 Failed in No Comparative rolling4776 20.1 4.0 0.04 0.014 0.296 x No Comparative 4774 20.2 5.1 0.05 0.0140.009 <0.01 x No Comparative 4773 19.7 4.8 0.02 0.004 <0.01 <0.01 x NoComparative 4772 12.2 3.6 2.5 0.003 <0.01 0.237 Failed in No comparativerolling 4799 20.0 2.8 1.87 0.023 0.017 0.281 x No Comparative 4800 14.93.0 1.9 0.022 0.013 0.296 x x (disclosure) 4855 10.1 3.8 1.96 0.0190.012 0.279 x x (disclosure) 4856 10.0 5.0 2.0 0.015 0.012 0.285 Failedin No Comparative rolling 4857 10.0 3.1 1.97 0.025 0.015 0.297 x x(disclosure) 4858 14.7 3.9 2.01 0.022 0.015 0.292 x x (disclosure) 485912.1 4.0 2 0.024 0.014 0.289 X x (disclosure) 4860 12.0 3.1 1.98 0.0160.014 0.284 X x (disclosure) 4861 10.0 4.0 1.99 0.015 0.015 0.29 X x(disclosure)

Thus, as can be seen from the table above, the alloys of the presentdisclosure shows good workability and good oxidation performance.

FIGS. 2 a) to e) disclose samples which are polished sections of of thepresent disclosure (FIGS. 2a ) 4783 and 2 b) 4779) compared to threecomparative alloys after exposure to 50 times 1 hour cycles at 850° C.exposed to biomass (wood pellets) ash containing large amounts ofpotassium. The micrographs are taken in a JEOL FEG SEM at 1000 timesmagnification and show a clear advantage in behavior between the alloysof the present disclosure and reference materials. As can be seen, onthe alloys of present disclosure, a 3-4 μm thin and protective aluminascale (aluminium oxide layer) has been formed, whereas a thicker andless protective chromia (chromium oxide) rich scale is formed on thestainless steel (2 c—11Ni, 21Cr, N, Ce, Fe bal.) and Ni-base alloy (2e—Inconel 625: 58Ni, 21Cr, 0.4Al, 0.5Si, Mo, Nb, Fe), and a relativelyporous and not as protective alumina scale forms on the comparativeFeCrAl alloy (alloy 4776) (FIG. 2d —20Cr, 5Al, 0.04 Si, Fe bal).

As can be seen from FIGS. 2a-e , the addition of Si, Al and Cr accordingto the ranges according to the present disclosure will promote aluminascale formation at Al levels as low as about 2 wt % and at chromiumlevels as low as 5 wt %.

1. A ferritic alloy comprising the following elements in weight % [wt %]C 0.01 to 0.1; N: 0.001 to 0.1; O: ≤0.2; Cr 4 to 15; Al 2 to 6; Si 0.5to 3; Mn: ≤0.4; Mo+W≤4; Y≤1.0; Sc, Ce, and/or La≤0.2; Zr≤0.40; RE≤1.0;balance Fe and normal occurring impurities and also fulfilling thefollowing equation has to be fulfilled (elements in weight fraction):0.014≤(Al+0.5Si)(Cr+10Si+0.1)≤0.022.
 2. The ferritic alloy according toclaim 1, wherein (elements in weight fractions)0.015≤(Al+0.5Si)(Cr+10Si+0.1)≤0.021
 3. The ferritic alloy according toclaim 1, wherein Zr is of from 0.05 to 0.40 weight %.
 4. The ferriticalloy according to claim 1, wherein Cr is of from 5 to 13 weight %. 5.The ferritic alloy according to claim 1, wherein Cr is of from 6 to 12weight %.
 6. The ferritic alloy according to claim 1, wherein Al is offrom 2.5 to 4.5 weight % or from 3 to 5 weight %.
 7. The ferritic alloyaccording to claim 1, wherein Al is of from 3 to 4 weight %.
 8. Theferritic alloy according to claim 1, wherein Si is of from 1.0 to 3weight %.
 9. The ferritic alloy according to claim 1, wherein Si is offrom 1.5 to 2.5 weight %.
 10. The ferritic alloy according to claim 1,wherein Zr is of from 0.10 to 0.35 weight %.
 11. The ferritic alloyaccording to claim 1, wherein the amount of C, N and Zr fulfills thefollowing equation:${- 0.15} \leq {{Zr} - \frac{{4.7C} + {4N}}{0.62}} \leq {0.15.}$
 12. Acoating comprising the ferritic alloy according to claim
 1. 13. Anobject comprising the ferritic alloy according to claim
 1. 14. Use ofthe ferritic alloy according to claim 1 for manufacturing a coatingand/or a cladding and/or an object.
 15. Use of the ferritic alloyaccording to claim 1 for manufacturing an object or a coating to be usedin corrosive environments.
 16. Use of the ferritic alloy according toclaim 1 for manufacturing an object or a coating to be used in a furnaceor as a heating element.
 17. Use of the ferritic alloy according toclaim 1 in environments wherein the ferritic alloy is exposed to salts,liquid lead and other metals, exposed to ash or high carbon contentdeposits, combustion atmospheres, atmospheres with low pO₂ and/or highN₂ and/or high carbon activity.
 18. The ferritic alloy according toclaim 2, wherein Zr is of from 0.05 to 0.40 weight %.
 19. The ferriticalloy according to claim 2, wherein Cr is of from 5 to 13 weight %. 20.The ferritic alloy according to claim 3, wherein Cr is of from 5 to 13weight %.